Fig. 3

Strong correlation of sugar residues in serum vs. CSF in controls, but much less in the MS group. a IgG1 afucosylation, bisecting GlcNAc, galactosylation, and sialylation strongly correlate in CSF vs. serum from control donors (blue circles) which do not have intrathecal IgG synthesis. In contrast, the correlation is much weaker within the MS group (orange triangles), consistent with additional intrathecal IgG synthesis. ϱ and p values (Spearman’s method, adjusted for multiple testing) are given for each sugar residue. Trendlines represent LOWESS lines (Cleveland 1979) and indicate the strength of association (Spearman’s ϱ) by their opacity and thickness. Dashed gray lines represent the angle bisectors, indicating where CSF and serum glycosylation would be equal. Thus, each data point that is located left/above this line indicates a sample pair where the respective feature is overrepresented in CSF, whereas each data point right/below this line indicates a sample pair where the respective feature is overrepresented in the serum. This is summarized schematically in b, showing that IgG1 is differentially glycosylated in CSF vs. serum. For selection of significant differences between CSF and serum, paired Wilcoxon tests were used with Bonferroni correction for multiple testing (see also Fig. 2). In MS patients (orange), bisecting GlcNAc were enriched in CSF, whereas CSF IgG1 was less sialylated and galactosylated compared to serum. In controls (blue), CSF IgG1 was also less galactosylated but contained more afucosylated IgG1 (p _adj < 0.01 for all)